1. Field of the Invention
The present invention relates to a reflecting mirror which reflects light, and in particular, to a reflecting mirror which is suitable as a door mirror, an interior mirror or the like mounted to a vehicle.
2. Description of the Related Art
Reflecting mirrors, which are called door mirrors (and sometimes called outer view mirrors) and which are for confirming the regions at the rear left and the rear right of a vehicle, are provided at a vehicle.
Confirmation of the regions at the rear of the vehicle in such a reflecting mirror is carried out by confirming the reflected image formed by the light reflected by the reflecting mirror. At night or the like, for example, due to the light of the headlights of a vehicle traveling behind being reflected in the reflecting mirror, it can be confirmed that there is a vehicle traveling behind.
However, at night or the like, the light of headlights are sufficiently bright with respect to the surrounding brightness, and the light reflected at the reflecting mirror is glaring. Thus, as disclosed in Japanese Patent Application Laid-Open (JP-A) No. 2001-330864, reflecting mirrors, in which an electrochromic covering film is provided between a glass substrate and a reflecting film, have sometimes been used as door mirrors and the like of vehicles in recent years.
The basics of the structure of a reflecting mirror 50 at which an electrochromic covering film 52 is provided are shown in cross-sectional view in FIG. 2.
As shown in FIG. 2, the reflecting mirror 50 is provided with a substantially transparent glass substrate 54. An electrically conductive reflecting film 56, which is shaped as a thin film and contains aluminum or the like, is formed on the rear surface of the glass substrate 54.
The electrochromic covering film 52 is disposed between the glass substrate 54 and the electrically conductive reflecting film 56. The electrochromic covering film 52 is structured by, for example and in order from the glass substrate 54 side, a transparent electrode 58 which is transparent and contains ITO (Indium Tin Oxide), an oxidation coloring film 60 formed of iridium oxide or the like, an ion conducting film 62 which contains tantalum oxide or the like and through which the passage of hydrogen ions is possible, and a reduction coloring film 64 formed of tungsten oxide or the like.
When a predetermined voltage is applied to the reflecting mirror 50 having this structure from the transparent electrode 58 side, hydrogen ions are released from the oxidation coloring film 60. The released hydrogen ions pass through the ion conducting film 62, and move to the reduction coloring film 64. Due to the hydrogen ions which have moved thereto, a reversible chemical reaction occurs at the reduction coloring film 64. The reduction coloring film 64 is thereby colored to, for example, a bluish color. Moreover, the oxidation coloring film 60 is colored, albeit slightly, due to the hydrogen being released. In this way, due to the reduction coloring film 64 and the oxidation coloring film 60 being colored, the transmittance of light at the electrochromic covering film 52 is reduced. Therefore, even if the light of headlights is incident on the reflecting mirror 50 as described above, the light amount of the reflected light can be reduced, and the ability to prevent glare can be improved.
Moreover, in this state in which the reduction coloring film 64 and the oxidation coloring film 60 are colored, when the aforementioned application of voltage is cancelled, or reverse voltage is applied, hydrogen ions are released from the reduction coloring film 64 and return toward the oxidation coloring film 60. Due to this reaction, the coloration of the reduction coloring film 64 and the oxidation coloring film 60 is cancelled, and the films 64, 60 return to their original states.
In the reflecting mirror 50 having the electrochromic covering film 52 as described above, five layers of thin films, which are the electrically conductive reflecting film 56, the transparent electrode 58, the oxidation coloring film 60, the ion conducting film 62 and the reduction coloring film 64 are needed. Accordingly, five film forming processes are required, and a problem arises in that the manufacturing costs are high.
Moreover, transmittance of light is greatly affected by the film thicknesses and the film qualities of the respective thin films. Accordingly, if the film thicknesses and the film qualities of all of the aforementioned five thin films are not managed, the product quality of the reflecting mirror 50 cannot be stabilized. In addition, if the oxidation coloring film 60 contains iridium oxide, it is not completely transparent even in the state before it becomes colored. Thus, the transmittance of light at usual times is low, and it is difficult to make large the difference between the transmittances of light before and after coloring.